In a driving mode test conducted by the use of a chassis dynamometer device, the vehicle driving mode display device is utilized. As shown in Japan Unexamined Patent Application Publication No. 11-160203, the vehicle driving mode display device displays a current actual speed on a running speed pattern that is previously determined by the driving mode so as to assist a test driver in driving the vehicle according to the running speed pattern.
The running speed pattern is displayed on a graph wherein time and speed are plotted on each axis. Since the running speed pattern has a tolerance range (for example, ±1 km/h, hereinafter also called as a tolerance area) and the tolerance area is expressed on the graph at the same time, the test driver drives the vehicle in such a way as to fall the actual vehicle speed in the tolerance area.
However, conventionally, a warning (an alarm) is issued for the test driver when the actual vehicle speed exceeds the tolerance range. This can be a warning about a state of continuously exceeding the tolerance range, however, it is not possible to avoid exceeding the tolerance range itself.